Nick Diaz is launching a fresh attempt to land a rematch with Georges St-Pierre, after his camp revealed an official complaint will be filed against the Quebec Athletic Commission over the weigh-in procedure for UFC 158.

Fighters in the UFC are typically allowed to weigh one pound over the legal limit at weigh-ins, but championship bouts dictate that the two rivals must hit the precise limit - in this case 170lbs.

However, a video has emerged of UFC executive Michael Mersch telling Diaz moments before the UFC 158 weigh-in that both he and St-Pierre would be allowed to tip the scales at anything up to 170.9lbs.

"They're going to allow you and Georges to have an extra hour. Just in case somebody doesn't make it," Mersch said. "But the good news is, they don't count the decimal. If you're 170.2, it's 170. If it's 170.9, it's 170."

Mersch added: "It's just something to keep in mind. That's kind of an off the record type of thing. But keep that in mind. As long as he's under 171, we should be good."

MMA Fighting have since published an email from Quebec Commission representative Joyce Tremblay revealing that "no contestants exceeded the weight determined in their contract" and that "our regulation does not take decimals into account".

However, the Diaz camp is attempting to use the grey area as leverage to force a rematch - after he played his part in hyping the fight into one of the UFC's best box-office showings of recent times.

"The Quebec Commission's statement is a disappointing admission that the March 16 event was not conducted under the rules applicable to a UFC title fight - or under the rules the fighters contractually agreed to, upon which rules Mr Diaz was entitled to rely under his bout agreement," said Jonathan Tweedale, a Diaz camp representative.

"Section 168 of the Regulation respecting combat sports provides that the maximum weight that a fighter must achieve at the official weigh-in shall be determined in advance by contract - and if the fighter does not make the contracted weight - in this case 170lbs - then 20% of his purse or 'the contestant's remuneration' will be deducted and paid to his opponent (subsections (7) and (8)). The contracted weight for this fight was 170lbs. 170.9 is not 170, anywhere in the world, for a title fight. There is no question what '170lbs' means, in the bout agreement, as a matter of contractual interpretation.

"The Quebec Commission deliberately relaxed the rule in this case and, by its own admission, allowed their hometown fighter to 'make weight' even if he weighed more than the contracted weight."

Tweedale was also quoted as saying by Yahoo Sports: "When you're cutting 20, 25lbs, that last pound is a bitch. Who knows if he could have made it? I know this: Georges would have gassed in that fight if he had tried to make weight. Nick said he couldn't believe the power moves that Georges was able to do in the fight. Would he have been able to do those if he had been forced to sweat off the rest of the weight?"

At no stage is proof offered that St-Pierre did, in fact, weigh in at 170.9lbs, or anything over the 170lb limit. However, the Diaz camp believes there is enough of a grey area to force the rematch.

"In the circumstances, Mr St-Pierre remains legally and ethically obligated to fight Mr Diaz at 170lbs or else vacate the belt in favour of those prepared to fight at welterweight."

President Dana White was contacted on the issue by Yahoo, who quoted a text reply from White saying: "If GSP weighed 170 or 170.9 doesn't change the fact that [Diaz] got dominated."